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Solid state 12th Maharashtra state board

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SOLID
STATE
12th HSC
PRESENTE
D BY:
FREYA
CARDOZO
PRESENTED BY: FREYA CARDOZO

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What are solids?
Crystalline and Amorphous solids
Types of solids
• Ionic solids
• Molecular solids
• Covalent
• Metallic ...

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Classification of Solids
Crystalline Solids Amorphous Solids
 Regularity and periodicity in
arrangement of constituent pa...

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Solid state 12th Maharashtra state board

  1. 1. SOLID STATE 12th HSC PRESENTE D BY: FREYA CARDOZO PRESENTED BY: FREYA CARDOZO
  2. 2. What are solids? Crystalline and Amorphous solids Types of solids • Ionic solids • Molecular solids • Covalent • Metallic solid Crystal lattic and Types of Bravais Lattice PRESENTED BY: FREYA CARDOZO
  3. 3. Classification of Solids Crystalline Solids Amorphous Solids  Regularity and periodicity in arrangement of constituent particles in solid  Long range order  All are anisotropic except cubic crystal structure  Have sharp M.P and B.P  Eg. KCl, NaCl, Diamond etc  Random arrangement of constituent particles in solid  Short range order  All are isotropic in nature  They boil or melt over a range of temperatures  Eg. Graphite, Glass, Sand etc PRESENTED BY: FREYA CARDOZO
  4. 4. What is Anisotropy?  Anisotropy is the property of a material which allows it to change or assume different properties when measured in different directions.  It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties like absorbance, refractive index, conductivity, tensile strength, etc PRESENTED BY: FREYA CARDOZO
  5. 5. What is Isotropy?  The phenomenon in which the physical property of a solid does not change when measured in any direction is called isotropy  Due to the random distribution of amorphous solid they show this property PRESENTED BY: FREYA CARDOZO
  6. 6. Which is a crystalline and which is amporhous? A B PRESENTED BY: FREYA CARDOZO
  7. 7. Questions  Distinguish between crystalline and amorphous solids  Define anisotropy and isotropy PRESENTED BY: FREYA CARDOZO
  8. 8. Isomorphism  Same crystal structure  Two or more substances the chemical Composition has the same atomic ratio.  For example (i) NaF and MgO (ii) NaNO3 and CaCO3 are isomorphous pairs, and have the same atomic ratios, 1:1 and 1:1:3, respectively, of the constituent atoms. PRESENTED BY: FREYA CARDOZO
  9. 9. Polymorphism • A single substance that exists in two or more forms or crystalline structures is said to be polymorphous. • formed under different conditions. • For example : Calcite and aragonite calcium carbonate; α-quartz, b-quartz and cristobalite- Silica • Polymorphism occuring in elements is called allotropy. For example: three polymorphic (allotropic) forms of carbon are diamond, graphite and fullerene. PRESENTED BY: FREYA CARDOZO
  10. 10. Types of Solids  Ionic  Covalent  Molecular  Metallic 1 2 3 4 Points to differentiation :- Particles in each, Type of interaction, Conductance, Hard/Brittle, Examples PRESENTED BY: FREYA CARDOZO
  11. 11. PRESENTED BY: FREYA CARDOZO
  12. 12. Questions  Solid that have same chemical ratio of atoms and same crystal structure are?  Give one eg of polymorphism seen in elements  Molecular solids are a. crystalline solids b. amorphous solids c. ionic solids d. metallic solids  What are the types of particles in each of the four main classes of crystalline solids ?  Distinguish between ionic solids and molecular solids. PRESENTED BY: FREYA CARDOZO
  13. 13. Definitions  Lattice is a geometrical arrangement of points in a three dimensional periodic array  Basis are any atoms or ions that are placed on lattice points  A crystal structure is obtained by attaching a constituent particle to each of the lattice points. Such constituent particles that are attached to the lattice points form the basis of the crystal lattice or space lattice  The smallest repeating structural unit of a crystalline solid is called unit cell. PRESENTED BY: FREYA CARDOZO +
  14. 14. 7 major types of crystals 1. Cu Cubic 3 Scc, Bcc, Fcc 2. Te Tetragonal. 2 Scc, Bcc 3. O Orthorhombic 4 Scc, Bcc, Fcc, Base.C. 4. Mo Monoclinic 2 * Scc, Base.C. 5. T Triclinic. 1 Scc 6. He Hexagonal 1 Scc 7. R Rhombic 1 Scc PRESENTED BY: FREYA CARDOZO Simple/Primitive - Scc Body centered - Bcc Face centered - Fcc Base centered* - Base.C. CuTe Our MoTHeR
  15. 15. Crytal Systems PRESENTED BY: FREYA CARDOZO
  16. 16. Types of unit cells Types of unit cell : There are four types of unit cells. Primitive or simple unit cell : In primitive unit cell, the constituent particles are present at its corners only.  Body-centred unit cell : In this type of unit cell, one constituent particle is present at the centre of its body in addition to the corner particles.  Face-centred unit cell : This unit cell consists of particles at the centre of each of the faces in addition to the corner particles. Base-centred unit cell : This unit cell consists of particles at the centre of any two of its opposite faces in addition to the corner particles. PRESENTED BY: FREYA CARDOZO Base Centered
  17. 17. Number of atoms per unit cell How many of these in a cube?? Corners= Faces= PRESENTED BY: FREYA CARDOZO
  18. 18. SCC PRESENTED BY: FREYA CARDOZO
  19. 19. Bcc  At corners and in the body there are atoms  corners contri 1/8 No of corner=8 Thus 1/8*8 = 1 atom utilized at corners 1 placed in the body Thus total is 1+1=2 atoms PRESENTED BY: FREYA CARDOZO
  20. 20. FCC Corners= 8 But 1 atom at one corner is shared by 8 Thus contri of one is 1/8 Thus no of atoms at each corners is 1/8*8=1 No of faces= 6 1 atom shared by 2 i.e at one face there is ½ atom So at 6 faces 6*1/2=3 Total atoms= 1+3 = 4 ..in fcc PRESENTED BY: FREYA CARDOZO
  21. 21. Chalo ab tum batao FCC mai kitna?? SCC mai kitna?? Bccc mai kitna?? PRESENTED BY: FREYA CARDOZO
  22. 22. OVERVIEW Scc Bcc Fcc Simple cubic Atoms at corners oly Body centered Atoms at corner+ body Face centered Atoms at corners plus faces 1 atom/particle 1c+1b=2 1c+3f=4 PRESENTED BY: FREYA CARDOZO
  23. 23. Questions  Calculate the number of atoms in fcc unit cell.  Cesium chloride crystallizes in cubic unit cell with Cl ions at the corners and a Cs⊕ ion in the centre of the cube. How many CsCl molecules are there in the unit cell?  2 A compound made of elements C and D crystallizes in fcc structure. Atoms of C are present at the corners of the cube. Atoms of D are at the centres of faces of the cube. What is the formula of the compound? PRESENTED BY: FREYA CARDOZO
  24. 24. Answers  C – corners = 8 corners x 1/8 is contribution of each = 1 atom  D – center of faces = 6 face x ½ contribution of each = 3 atom  Thus, C1D3 is the formula of the crystal. PRESENTED BY: FREYA CARDOZO
  25. 25. • Packaging of solids • Derivation to calculate Density • Calculating No.of particles, unit cells And No.of unit cells in a given Volume • Type 1 numericals PRESENTED BY: FREYA CARDOZO
  26. 26. Derivation PRESENTED BY: FREYA CARDOZO
  27. 27. Formula :- d= nM/a3 NA PRESENTED BY: FREYA CARDOZO
  28. 28. Type 2 numericals When gold crystallizes, it forms face-centred cubic cells. The unit cell edge length is 408 pm. Calculate the density of gold. Molar mass of gold is 197 g/mol. PRESENTED BY: FREYA CARDOZO
  29. 29.  An element with molar mass 27 g/mol forms cubic unit cell with edge length of 405 pm. If density of the element is 2.7g/cm3.What is the nature of cubic unit cell? PRESENTED BY: FREYA CARDOZO
  30. 30. Relationships PRESENTED BY: FREYA CARDOZO
  31. 31. An element has a bcc structure with unit cell edge length of 288 pm.Density of the element is 7.2 g/cm3. How many unit cells and number of atoms are present in 200 g of the element? PRESENTED BY: FREYA CARDOZO
  32. 32. Niobium forms bcc structure. The density of niobium is 8.55 g/cm3 and length of unit cell edge is 330.6 pm. How many atoms and unit cells are present in 0.5 g of niobium PRESENTED BY: FREYA CARDOZO
  33. 33. Packing of particles in crystal lattice  Particles of a crystalline solid are close packed.  During packing all atoms are considered as hard spheres  Closer the packaging stronger the interparticle force of attraction. More strong and stable the crystal is.  Coordination number -The number of neighbouring spheres that touch any given sphere is its coordination number  Larger the magnitude of C.N more closely packed atoms, more compact is the crystal. PRESENTED BY: FREYA CARDOZO
  34. 34. Packaging  1D packing – linear arrangment of spheres  2D packing can be done in 2 ways 1. square 2. Hexagonal  placing layer two exactly over Layer 1 – both layers same i.e AA type  placing layer two in between the voids of layer 1- different layers i.e AB type Calculate coordination numbers!! PRESENTED BY: FREYA CARDOZO 1D AA Type AB type
  35. 35.  3D packaging - Stacking of two dimensional layers gives rise to three dimensional crystal structures.  Two dimensional square close packed layers are found to stack only in one way to give simple cubic lattice.  Hexagonal close pack can be found in 2 types  ABAB i.e HCP  ABCABC i.e ccp PRESENTED BY: FREYA CARDOZO
  36. 36. Simple cubic or primitive Cubic unit cell (SC) Eg. Polonium Each sphere is surrounded by 6 neighbouring spheres, 4 in its own layer, 1 above and 1 below. Hence coordination number of any sphere in sc is 6. PRESENTED BY: FREYA CARDOZO
  37. 37. Placing 3rd layer on hexagonal close pack PRESENTED BY: FREYA CARDOZO
  38. 38. PRESENTED BY: FREYA CARDOZO
  39. 39. Voids Tetrahedral Voids Coordination number = 4 PRESENTED BY: FREYA CARDOZO
  40. 40. Octahedral voids Coordination number=6 PRESENTED BY: FREYA CARDOZO
  41. 41. VOIDS Number of voids per atom in hcp and ccp : The tetrahedral and octahedral voids occur in hcp and ccp/fcc structures. There are two tetrahedral voids associated with each atom. The number of octahedral voids is half that of tetrahedral voids. Thus, there is one octahedral void per atom. If N denotes number of particles, then number of tetrahedral voids is 2N and that of octahedral voids is N. PRESENTED BY: FREYA CARDOZO
  42. 42. ABAB type –hcp Mg, Zn PRESENTED BY: FREYA CARDOZO
  43. 43. Ccp/fcc- ABCABC type Eg.Cu and Ag PRESENTED BY: FREYA CARDOZO
  44. 44. hcp and ccp/fcc structures that result from stacking of hexagonal close packed layers in two different ways, each sphere is surrounded by 12 neighbouring spheres, 6 in its own layer, 3 above and 3 below. Hence, the coordination number of any sphere in hcp or ccp/fcc structure is 12. PRESENTED BY: FREYA CARDOZO
  45. 45. Questions vi. Which of the following is not correct? a.Four spheres are involved in the formation of tetrahedral void. b. The centres of spheres in octahedral voids are at the apices of a regulaR Tetrahedron. c.If the number of atoms is N the Number of octahedral voids is 2N. d. If the number of atoms is N/2, the Number of tetrahedral voids is N. vii. A compound forms hcp structure. Number of octahedral and tetrhedral voids in 0.5 mole of substance is respectively a. 3.011×1023, 6.022×1023 b. 6.022×1023, 3.011×1023 c. 4.011×1023, 2.011×1023 d. 6.011×1023, 12.022×1023 PRESENTED BY: FREYA CARDOZO
  46. 46. Type 1 Numericals  A compound made of elements C and D crystallizes in fcc structure. Atoms of C are present at the corners of the cube. Atoms of D are at the centres of faces of the cube. What is the formula of the compound?  A compound is formed by two elements A and B.The atoms of element B forms ccp structure. The atoms of A occupy 1/3rd of tetrahedral voids. What is the formula of the compound ?  In an ionic crystalline solid atoms of element Y form hcp lattice. The atoms of element X occupy one third of tetrahedral voids. What is the formula of the compound ? PRESENTED BY: FREYA CARDOZO
  47. 47. A compound forms hcp structure. What is the number of (a) octahedral voids (b) tetrahedral voids (c) total voids formed in 0.4 mol of it. PRESENTED BY: FREYA CARDOZO
  48. 48. Recap: Stochiometric Defects 1. Vacancy defects 2. Self Interstitial impurity D. 3. Schottky D. 4. Frenkel D. PRESENTED BY: FREYA CARDOZO
  49. 49. disorders or irregularities in the stacking of atoms. Such irregularities in the arrangement of constituent particles of a solid crystal are called defects or imperfections. Why do these detects occur? Due to improper crystallization – Faster process or impurities present Majorly 3 types • point • Line • Plain PRESENTED BY: FREYA CARDOZO
  50. 50. Point DeFects -These defects are irregularities produced in the arrangement of basis at lattice points in crystalline solids.  Stoichiometric point defect  Impurity defect  Non-stoichiometric point defect PRESENTED BY: FREYA CARDOZO
  51. 51. Stoichiometric defect  What is stiochiometry Chemical formula of a compound shows fixed ratio of number of atoms or number of cations and anions. This fixed ratio is the stoichiometry of the compound.  Stiochometry unchanged. I.e same no of cation or anion or atoms as per mol.formula  Types 1. Vacancy defect 2. Self interstitial defect in elemental solid 3. Schottkydefect 4. Frenkel defect PRESENTED BY: FREYA CARDOZO
  52. 52. Vacancy defect. Self interstitia D.  particle is missing from its regular site in the crystal lattice. The missing particle creates a vacancy in the lattice structure  vacancy defect be developed during crystallization or when the substance is heated.  Since particle is missing, mass decreases  Volume unchanged  Density decreases  When some particles of a crystalline elemental solid occupy interstitial sites in the crystal structure, it is called self interstitial defect.  This happens in 2 ways 1. An extra atom sits in interstitial space. Remaining atoms r in their own space. Since, 1 extra particle 2. Mass increases and Density increases 3. One of the atom from the crystal leaves its own position and occupies interstitial space. Since no atom is lost or gained. Mass same this density unchanged PRESENTED BY: FREYA CARDOZO
  53. 53. Schottky defect  Its a type of bacany defect seen in an ionic solid  A cation and anion are missing from their regular position. Loss of either one leads to loss of the other also so that electrical neutrality is maintained.  Thus, there exist two holes per ion pair lost, one created by missing cation and the other by a missing anion. Such a paired cation-anion vacancy defect is a Schottky defect.  Condition for formation 1. High degree of ionic character 2. High coordination number of anion 3. small diff in size of Cation n anion PRESENTED BY: FREYA CARDOZO
  54. 54.  Consequence 1. since ions are missing mass decreases thus density decreases 2. Electrical neutrality maintained Eg. NaCl, AgBr and KCl. PRESENTED BY: FREYA CARDOZO
  55. 55. Frenkel defect  Frenkel defect arises when an ion of an ionic compound is missing from its regular lattice site and occupies interstitial position between lattice points.  Cations are usually smaller than anions. It is, therfore, more common to find the cations occupying interstitial sites.  Smaller cation is displaced from its normal site to an interstitial space. It, therefore, creates a vacancy defect at its original position and interstitial defect at its new location in the same crystal.  Frenkel defect can be regarded as the combination of vacancy defect and interstitial defect. PRESENTED BY: FREYA CARDOZO
  56. 56.  Conditions 1. Ions having low coordination numbers 2. Large difference in sizes of cation n anions  consequences 1. As no ions are missing from the crystal lattice as a whole, the density of solid and its chemical properties remain unchanged. 2. Electrical neutrality maintained  Eg.. ZnS, AgCl, AgBr, AgI, CaF2 PRESENTED BY: FREYA CARDOZO
  57. 57. Impurity defect  Impurity defect arises when foreign atoms, that is, atoms different from the host atoms, are present in the crystal lattice.  They are of two types 1. Substitutional impurity defect  Solid solutions of metals (alloys)  Vacancy through aliovalent impuriy 2. Interstitialal impurity defect PRESENTED BY: FREYA CARDOZO
  58. 58. Substitution impuriy defects  In this defect, the foreign atoms are found at the lattice sites in place of host atoms.  The regular atoms are displaced from their lattice sites by impurity atoms. Solid solution of Metal (alloy) Eg. Brass( made of Cu with impurity of Zn) Vacancy through Aliovalent impurity Vacancies are created by the addition of impurities of aliovalent ions (that is, ions with oxidation state (o.s.) different from that of host ions) to an ionic solid. Impurity of SrCl2 in NaCl…Sr2⊕ ions Occupy some of the regular sites of Na⊕ host . To maintain electrical neutrality, Sr2⊕ ion removes two Na⊕ions. One of the vacant lattice sites created by removal of two Na⊕ ions is occupied by one Sr2⊕ ion. The other site of Na⊕ ion remains vacant PRESENTED BY: FREYA CARDOZO
  59. 59. Interstitial Impurity defect In this defect, the impurity atoms occupy interstitial spaces of lattice structure. For example in steel, Fe atoms occupy normal lattice sites. The carbon atoms are present at interstitial spaces, PRESENTED BY: FREYA CARDOZO
  60. 60. Nonstoichiometric defects  Stochiometry is disturbed  stoichiometry does not cause any change in the crystal structure.  Nonstoichiometric defect arises when the ratio of number of atoms of one kind to that of other kind or the ratio of number of cations to anions becomes different from that indicated by its chemical formula  Two types 1. Metal deficiency defect Eg. NiO and Ni0.97O1.0 2. Metal excess defect  A neutral atom or an extra positive ion occupies interstitial position –ZnO and Zn1+xO1.0  By anion vacancies (Colour or F-centres) – NaCl and Na1+xCl1.0 PRESENTED BY: FREYA CARDOZO
  61. 61. Metal deficiency defect  In compounds with variable oxidation states  The cation from such compounds is missing  The excess negative charge created due to this is balanced by presence of cation of the same metal with higher oxidation state than that of missing cation.  Eg. NiO, Ni2+ and O-2  One Ni2+ is missing the excess charge is balanced By two Ni3+ atoms. Stochiometry actually is Ni0.97O1.0 PRESENTED BY: FREYA CARDOZO
  62. 62. Metal excess defect: A neutral atom or an extra positive ion occupies interstitial position PRESENTED BY: FREYA CARDOZO Thus the Non- stoichiometri c formula is Zn1+xO1.0
  63. 63. Metal excess defect:By anion vacancies (Colour or F-centres)  This type of non stoichiometric defect imparts colour to solid  Eg. When NaCl is heated in atmosphere of Na, the Cl ions from the crystal come to the surface and react with the Na to form NaCl at the surface.  the reaction with Na at the surface releases an electron that occupies The vacant spaces created by the Cl ions.  The anion vacant sites occupied by electrons are F-centres or colour center  crystal this has extra Na atom  Formula- Na1+xCl1.0 PRESENTED BY: FREYA CARDOZO
  64. 64. PRESENTED BY: FREYA CARDOZO
  65. 65. 13. Explain with diagram, Frenkel defect. What are the conditions for its formation? What is its effect on density and electrical neutrality of the crystal? 14. What is an impurity defect? What are its types? Explain the formation of vacancies through aliovalent impurity lwith example. What are the consequences of Schottky defect? iii. In Frenkel defect a. electrical neutrality of the substance is changed. b. density of the substance is changed. c. both cation and anion are missing d. overall electical neutrality is preserved. PRESENTED BY: FREYA CARDOZO
  66. 66. Electrical properties of solids  CONDUCTORS 1. Solids having electrical conductivities in the range 104 to 107 Ohm-1m-1are called conductors. 2. Metals and electrolytes (ionic solids) are examples of electrical conductors. 3. Metals conduct electricity by movement of electrons while electrolytes conduct electricity by movement of ions.  INSULATORS 1. Solids having low electrical conductivities in the range 10-20 to 10-10 Ohm-1m-1 are called insulators. 2. Most nonmetals and molecular solids belong to this category.  SEMICONDUCTORS 1. Solids having electrical conductivities in the range 10-6 to 104 Ohm-1 m-1 are semiconductors. 2. This range is intermediate between conductors and insulators. 3. Metalloids like silicon, germanium belong to this category. PRESENTED BY: FREYA CARDOZO
  67. 67. Used to explain the classification of substances as metals, non metals and metalloid PRESENTED BY: FREYA CARDOZO
  68. 68. Band theory  A band is made of closely spaced electronic energy levels.  Band formation can be correlated to formation of molecular orbitals (MOs) by interaction of atomic orbitals  According to MO theory interaction of atomic orbitals of combining atoms results in formation of equal number of MOs which spread over the entire molecule.  Similar to this, interaction of energy levels of electrons in the closely spaced constituent atoms in solids result in formation of bands. PRESENTED BY: FREYA CARDOZO
  69. 69. Types of band 1. Conduction band  The highest energy band containing electrons is the conduction band.  It is formed by interaction of the outermost energy levels of closely spaced atoms in solids.  Conduction band may be partially occupied or vacant.  Electrons in conduction band are mobile and delocalized over the entire solid  They conduct electricity when potential is applied PRESENTED BY: FREYA CARDOZO
  70. 70. Valence band  The band having lower energy than conduction band is the valence band.  The electrons in valence band are not free to move because they are tightly bound to the respective nuclei. PRESENTED BY: FREYA CARDOZO
  71. 71. Band gap  The energy difference between valence band and conduction band is called band gap.  Size of the band gap decides whether electrons from valence band can be promoted to vacant conduction band or not  when band gap is too large to promote electrons from valence band to vacant conduction band by thermal energy, it is called forbidden zone.  When band gap is small, electrons from higher energy levels in valence band can be promoted to conduction band by absorption of energy (such as thermal, electromagnetic). PRESENTED BY: FREYA CARDOZO
  72. 72. Insulators  Valence band is completely filled with electrons and the conducation band is empty  Both bands are seperated by separated a large energy gap called forbidden zone  Thermal energy is insufficient to promote electrons PRESENTED BY: FREYA CARDOZO
  73. 73. Conductors  Outermost electrons of all the atoms in the metallic crystal occupy conduction band.  The number of electrons in conduction band of metals is large. Hence metals are good conductors of electricity  Depending on which orbitals are involved in the formation of band they are labbeled as s band p band  Band formation in metallic conductors, thus, results in delocalization of the outermost electrons of all the metal atoms leaving behind metal ions.  This is described as 'cations of metal are immersed in the sea of electrons'. PRESENTED BY: FREYA CARDOZO
  74. 74.  Give reason : conductivity of metals decreases with increase in temperature Metal cations occupying lattice positions in the crystal are always in vibrational motion When thermal energy is applied the vibrational motion increases greatly due to which the Flow of electrons is interrupted Thus,… PRESENTED BY: FREYA CARDOZO
  75. 75. Semiconductor  Intermediate between CONDUCTORS and insulators  The valence band in semiconductor is completely filled with Electrons and conduction band is empty. However, the energy gap between the two bands is smaller than that in an insulator.  At a temperature above absolute zero a few electrons in the valence band have enough thermal energy to jump through the small band gap and occupy higher energy conduction band.  The conduction band, thus, becomes partially filled and the valence band becomes partially empty.  Thus when potential is applied more es are promoted to the conduction band  Eg. Si and Ge PRESENTED BY: FREYA CARDOZO
  76. 76. Intrinsic Semiconductors At a temperature above absolute zero a few electrons in the valence band have enough thermal energy to jump through the small band gap and occupy higher energy conduction band. The conduction band, thus, becomes partially filled and the valence band becomes partially empty. PRESENTED BY: FREYA CARDOZO
  77. 77. Extrinsic Semiconductors  The conductance of an extrinsic Semiconductor can be increased by adding minute small amount of impurities by a process called doping  the added impuriy is called a dopant  A doped semiconductor, having higher conductivity than pure intrinsic semiconductor, is an extrinsic semiconductor  These are of 2 types 1. n type 2. p type PRESENTED BY: FREYA CARDOZO
  78. 78. Extrinsic conductors n type p type  Doped with grp 15 elements  Charge carriers are electrons  Eg. Si doped with P  Extra electron from P, this helps increase electrons in conduction band  Contain More number of valence electrons that of the pure semiconductor.  Dopped with grp 13 elements  Charge carriers are holes which behave as positive charge  Si doped with B  One electron less than what is required to bond with Si  Contain less number of valence electrons than that of the pure semiconductor. PRESENTED BY: FREYA CARDOZO
  79. 79. P type  Impurity from group 13  Boron atom has only three valence electrons. It does not have enough electrons to form bonds with its four Si neighbours.B atom forms bonds with three Si atoms only. The missing fourth electron creates an electron vacancy. It is called a hole.  A hole has a tendency to accept electron from its close vicinity. Thus, a hole behaves as if it has a positive charge.  The electrons in partially filled valence band move under the influence of an applied potential. Theholes move in the opposite direction  Because the charge carriers are holes which behave like positive charge, the Si or Ge doped with group 13 element semiconductoor In, is a p-type semiconductor. PRESENTED BY: FREYA CARDOZO
  80. 80. N type  Si has a crystal structure in which each Si atom is linked tetrahedrally to four other Si atoms  When P is added it occupies places in the lattice  Four of the five valence electrons of P are utilized in bonding the closest to four Si atoms. Thus, P has one extra electron than needed for Bonding  Because the charge carriers are the increased number of electrons, Si or Ge doped with group 15 elements such as P, As, Sb or Bi is an n-type semiconductor. PRESENTED BY: FREYA CARDOZO
  81. 81. PRESENTED BY: FREYA CARDOZO
  82. 82. Question ii. Which of the follwong is n-type semiconductor? a. Pure Si b. Si doped with As c. Si doped with Ga d. Ge doped with In PRESENTED BY: FREYA CARDOZO
  83. 83. Magnetic properties of solids  Electrons spin about their own axis due to which a magnetic field is induced  Thus electrins act as tiny magnets  If electrons are unpaired i.e single e in an orbital it will contribute to magnetic field  But paired es cancel each other’s spin this no magnetic field is generated  3 types of magnetism 1. Diamagnetic 2. Paramagnetic 3. Ferromagnetic PRESENTED BY: FREYA CARDOZO
  84. 84. Dimagnetic  All electrons paired  Electrons weakly replled by magnetic fields  Pairing of electrons balances the spins and hence, cancels their magnetic moments.  N2, F2 ,NaCl, H2O and benzene are some examples of diamagnetic substances. PRESENTED BY: FREYA CARDOZO
  85. 85. Paramagnetic  The substances with unpaired electrons  Weakly attracted by Magnetic field  The spinning of unpaired electron gives rise to a magnetic moment. The substance is attracted by magnetic field because of magnetic moment.  These substances exhibit magnetism in Presence of external magnetic field only. They Lose magnetism when the external magnetic field is removed.  Oxygen, Cu2⊕, Fe3⊕, Cr3⊕ are some examples of paramagnetic substances. PRESENTED BY: FREYA CARDOZO
  86. 86. Ferromagnetic  large number of unpaired electrons  attracted strongly by magnetic field  These substances can be permanently magnetised. They retain magnetism even after the removal of external magnetic field.  Some example of ferromagnetic substances are Fe, Co, Ni, Gd, CrO2 PRESENTED BY: FREYA CARDOZO
  87. 87. Packaging efficiency like Coordination number indicates the Measure of how tightly solids are packaged PRESENTED BY: FREYA CARDOZO
  88. 88. Packaging efficiency calculation  Formula PRESENTED BY: FREYA CARDOZO
  89. 89. Scc(simple cubic)n=1 a = 2r or r = a/2 PRESENTED BY: FREYA CARDOZO
  90. 90. PRESENTED BY: FREYA CARDOZO
  91. 91. Bcc (Body Centered cubic) n=2 FED and AFD PRESENTED BY: FREYA CARDOZO
  92. 92. PRESENTED BY: FREYA CARDOZO
  93. 93. FCC(Face centered cubic) n=4 The triangle ABC is right angled with ∠ABC = 90 AC PRESENTED BY: FREYA CARDOZO
  94. 94. PRESENTED BY: FREYA CARDOZO
  95. 95. PRESENTED BY: FREYA CARDOZO
  96. 96. PRESENTED BY: FREYA CARDOZO
  97. 97.  coordination number PRESENTED BY: FREYA CARDOZO
  98. 98. Same as ccp and hcp PRESENTED BY: FREYA CARDOZO
  99. 99. vii. Pb has fcc structure with edge length of unit cell 495 pm. Radius of Pb atom is a. 205 pm b. 185 pm c. 260 pm d. 175 pm  Cu crystallizes in Bcc unit cell with edge length of 495 pm. What is the radius of Cu atom? PRESENTED BY: FREYA CARDOZO
  100. 100. The unit cell of metallic silver is fcc. If radius of Ag atom is 144.4 pm, calculat (a) edge length of unit cell (b) volume of Ag atom, (c) the percent of the volume of a unit cell, that is occupied by Ag atoms, (d) the percent of empty space. PRESENTED BY: FREYA CARDOZO
  101. 101. 4. The density of iridium is 22.4 g/cm3. The unit cell of iridium is fcc. Calculate the radius of iridium atom. Molar mass of iridium is 192.2 g/mol. 5. Aluminium crystallizes in cubic close packed structure with unit cell edge length of 353.6 pm. What is the radius of Al atom? How many unit cells are there in 1.00 cm3of Al? (125 pm, 2.26×1022) PRESENTED BY: FREYA CARDOZO

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